The classic problem of stability and transition to turbulence of an incompressible flow over a flat plate subjected to uniform suction through the surface is considered. This is an important “model” problem for laminar flow control and the results have direct application to the design of low drag aerofoils. Detailed mean boundary layer calculations are presented and the flow stability is determined by obtaining numerical solutions of the Orr-Somerfield equation. Transition conditions are estimated by using the semi-empirical en method. Accurate values have been obtained for the levels of suction necessary to delay instability and transition indefinitely. Consideration has also been given to the effect of surface suction upon the plate drag.

This paper develops the theory of turning flight in a moving air mass to explain some of the problems encountered in making downwind turns, particularly in light aircraft. Although the basic mechanics of flight and aerodynamics of the aircraft are well understood, the methods used by the pilot to control the aircraft in turning flight are less well established and can be critical in maintaining a safe flight path. In this paper the effect of the control strategy likely to be employed by a pilot flying close to the ground is used to show how the energy loss during a turn can lead to an unsafe flight path.

This paper describes the use of oct-trees to represent digitised terrain elevation data (DTED) in terrain reference navigation (TRN) systems. Oct-trees provide a regular method to represent digitised terrain data where the level of detail of the terrain is encoded in the tree structure. The use of oct-trees also provides a basis for a significant reduction in the on-line storage requirement for DT-EDs. A method of encoding using Morton ordering is introduced which allows DTEDs to be accessed as oct-trees and quad-trees where the tree structures are represented as pointerless structures. Algorithms to construct and access terrain oct-trees are presented which form a set of access primitives for tree operations required in TRN applications. The paper concludes with examples to illustrate the efficiency of the methods described in the paper for two DTEDs, in terms of performance of the tree access operations and reductions in storage.

The paper examines the influence on optimal structural designs of changing the finite element selection, the structural design criteria and the design concepts for an unmanned air-vehicle wing. Thus, single and twin-spar designs are considered with a number of composite design configurations. The results indicate that some of the design criteria have little influence on the optimal designs whilst finite element selection can be significant.

The factors influencing survival in aircraft accidents can be classified into configurational, environmental, procedural or behavioural. New methodologies which have been developed in order to simulate emergency behaviour are introduced. A series of experimental programmes in which the new behavioural techniques are applied to configurational, environmental and procedural changes in the cabin are described. The results suggest that the techniques provide the behavioural and statistical data required for the assessment of design options or safety procedures for use in aircraft emergencies.

A computer assisted conceptual aircraft design methodology (CACAD) has been developed to size turbofan powered transport aircraft. New modules for predicting the maintenance costs of each airframe system and subsection of structure, were developed and incorporated into CACAD.

Many aspects of variable camber wing technology (VCW) were modelled. These included different types of drag saving due to chordwise, as well as spanwise camber variation. Models were also derived for mass, maintenance cost, and extra development cost increments for wing trailing edge devices, flight control, and hydraulic systems. These were incorporated into CACAD, and then a multidisciplinary trade-off study resulted in predicted savings of up to 3·5% in direct operating cost (DOC). The technology was evaluated for DOC improvement against a number of existing, future, and derivative aircraft, under different sensitivity conditions. Reliability, maintainability, and development (R, M&D) predictions were shown to be decisive in determining the feasibility of VCW technology. The study showed that long range, low to medium capacity, derivative aircraft are the most suitable applications for VCW technology.